The present invention is directed to a device for the protection of surfaces exposed to marine environments, and is particularly related to the provision of coatings for marine structures which provide anti-foulant protection.
One of the major problems attending the maintenance of surfaces in contact with marine environments has been the prevention of incrustation and corrosion resulting from the attachment or other contact of marine plant and animal life thereto. Specifically, the growth of barnacles and other marine organisms has posed a significant maintenance problem, as the cleaning and removal of such incrustations comprises a costly, time-consuming procedure. As an attempt to reduce or otherwise ameliorate the difficulties attending the growth of such incrustations, anti-fouling coatings comprising materials known to be toxic to marine life have been applied in various manners to such structures as ships' hulls and the like. Specifically, such coatings have comprised sheets prepared from metals having known toxicity to marine life, such as copper and the like. Other approaches have comprised the employment of paint-like coatings incorporating within certain toxic ingredients.
In recent years, efforts to retard marine fouling have focused on the development of improved paint vehicles for dispersing the familiar toxic salts therein. Inasmuch as the most effective marine anti-fouling toxics are generally chemically insoluble in most useful paint vehicles, the toxic is either leached rapidly from the typical paint film, or the paint film is designed to expose the toxic to the sea water. In either case, the effective foul-free life is limited, and the cost of using such paints on an object such as a ship's hull or any permanently submerged object is exceedingly high.
Additionally, the conventional paint coatings tend to promote barnacle growth after the expiration of the toxic therefrom. Thus, when replacement and re-coating are required, an expensive maintenance schedule must be followed wherein the marine surface must first be scrapped or otherwise cleaned to provide the appropriate surface for a re-coating operation. The process of cleaning and re-coating the marine surface is extremely time-consuming and costly, as the marine growths develop on the painted surface in concentrations comparable to those encountered on uncoated surfaces.
The development of the aforenoted incrustations serves to degrade the surface of the particular structure, and in the case of sea-going vessels, tends to reduce the ability of the vessel to move efficiently in water with the result that additional cost in fuel and time are occasioned.
The employment of sheet-like coating is recognized in the prior art as an alternative to the provision of painted anti-fouling compositions. Specifically, U.S. Pat. No. 3,761,334, to Zondek discloses an anti-fouling sheet-like coating comprising a metal foil which is applied to the surface by a pressure-sensitive or heat-sensitive adhesive or the like. The Zondek coating is a permanent coating, as it is intended that the metal surface of the foil will indefinitely provide the desired anti-fouling capability. Although the Zondek sheet appears to provide anti-fouling protection, the additional weight occasioned by the provision of such a metal foil coating would appear to detract from the economic value of indefinite application, as the additional weight would result in higher costs of operation in the case of sea-going vessels, particularly of a commercial nature. Moreover, the provision of a metal coating of the nature disclosed in Zondek could, in the instance where the surfaces to be protected are prepared from metal, promote an active site of galvanic corrosion which could occasion repairs to said surfaces far exceeding the cost and effort involved in the removal of the marine growths sought to be prevented.